The present invention relates to optical recording of data and in particular to the recording of data on a moving optical tape using a focussed laser beam.
One of the problems in scanning optical tape is that most prior art scanners use a rotary motion of the scanning element. This rotary motion generates a curved scan and the two methods proposed to rectify this condition are use of a field flattening lens, as shown in U.S. Pat. No. 4,168,506 and others or curving on the tape, for example, as shown in U.S. Pat. No. 3,874,621. The field flattening lens limits the maximum numerical apperture which can be used, thus limits the smallest spot size achievable and limiting the optical storage density. Curving the tape makes it difficult to control its movement to the degree of accuracy required in high density optical data storage.
The current invention generates an orthogonal scan by scanning linearly across a slow moving tape. Since the tape stays flat its motion can be precisely controlled. Since the focussing lens is used on its optical axis a large numerical apperture can be used yielding very high data storage densities. A further advantage of this invention is driving the scanner at its resonant frequency, a method requiring a very small amount of power to achieve a large movement.